Optimal Design of an Integrated Discontinuous Water-Using Network Coordinating with a Central Continuous Regeneration Unit

Abstract

A systematic approach is proposed to design an optimal batch water-using network with centralized regeneration in order to deal with coordination of discontinuous water-using operations with one central continuous regeneration unit during multiple repeated batch cycles. The mathematical formulation in weak forms that readily induces process dynamic expressions is established under the framework of continuous time representation, in which a rigorous dynamic model of a tank is embedded. The freshwater consumption and the regeneration flow rates are minimized by a two-stage optimization approach. The integration of the batch water-using system highlights fixed regeneration flow rates and transitional behaviors from the start-up phase to steady state in multiple batch cycles. Optimal network structures and evolution characteristics of residual water and contaminant concentrations in buffer tanks can be achieved through solutions to the nonlinear programming problems (NLP). Four scenarios, including truly batc...